Geotextiles are fabrics which are used in road, dam, river, drainage and ocean construction sites for preventing erosion on river banks and seashores, and around piers and bridges, in paving of roads and as filtration fabrics in dam construction and as silt retainers to prevent erosion at construction sites. Geotextiles prevent the movement of soil or sand when placed in contact with the ground. When used in paving roads, geotextiles help maintain structural integrity of the road surface.
Woven and nonwoven geotextile fabrics are known. Nonwoven geotextiles are used in applications which require higher filtration capability than is obtainable with woven geotextiles, and large widths are necessary. Moreover, the high absorbancy of nonwoven geotextiles promotes adhesion to road surfaces and flow resistance to water. Geotextile fabrics of woven construction are used in applications requiring higher strength and structural stability than is obtainable with nonwoven geotextiles.
Nonwoven geotextiles which are reinforced with a woven backing are also known. For example, see U.S. Pat. Nos. 3,928,696 and 4,002,034.
In producing a geotextile fabric, it is particularly desirable to have controlled strength and controlled elongation, with high tear resistance and proper filtration also being highly desirable. According to the present invention, a geotextile fabric is produced that has excellent tear resstance, and very precisely controlled elongation and strength. For some particular uses of the geotextile fabric according to the invention, the extensibility is about 2 to 4%, making the fabric useful for solving "reflective cracking" problems in paving and the like.
The geotextile fabric according to the present invention basically comprises first and second groups of parallel synthetic threads, the two groups being arranged substantially transverse to each other, and preferably are truly perpendicular. Knit yarn stitch bonds the first and second group of threads loosely together. The threads are preferably uncrimped synthetic yarns, either continuous thread yarn or spun yarn. A nonwoven web may also be incorporated in the geotextile fabric, being stitch bonded to the first and second groups of threads. Thus, the geotextile fabric according to the present invention does not have the adhesive found in many prior geotextiles, does not have the fiber damage often accompanied with needle punched nonwovens, and doesn't require the heat-bonding of other prior fabrics. Only the basic yarn elongation is a factor in the fabric elongation so that it is precisely controllable, and since the interlacings and interweavings of warp and weft yarns as is provided in normal laid-in woven fabrics is not present, the geotextile fabric of the invention has extremely high tear resistance.
For road paving uses in particular, the yarn and web types comprising the preferred geotextile fabric are controlled so that the fabric has an extensibility of about 2 to 4% or less. This then makes the fabric ideal for repairing surfaces having cracks therein by placing a layer of geotextile fabric on a cracked surface, and placing a layer of asphalt on top of the geotextile fabric. This same basic procedure can be followed in reinforcing asphalt surfaces when they are laid, by laying a first layer of asphalt, placing the geotextile fabric on the first layer, and placing a second layer of asphalt on top of the geotextile fabric. In the instances cited above the geotextile fabric is saturated with a suitable quantity of liquid asphalt binder which acts as a sealant and adhesive between the layers of asphalt.
The method to making the geotextile fabric according to the present invention is readily practiced using horizontal weft insertion, and warp insertion, type knit-stitching machines, such as those produced by Liba and Mayer.
It is the primary object of the present invention to provide a geotextile fabric, and methods of utilization and production thereof, with precisely controllable properties. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.